Clinical Health Updates

Varicella immunity wanes in children after 5 years

Clinical Question:
Does immunity from varicella vaccine decrease over time?

Bottom Line:
Immunity from varicella vaccination decreases over time, resulting in more cases of greater severity among older children. These data are the basis for the recommendation that children between the ages of 4 years and 6 years receive a second varicella vaccination. Thats why a second dose of varicella vaccine now recommended for all children, could improve protection from both primary vaccine failure and waning vaccine-induced immunity

Reference:
Chaves SS, Gargiullo P, Zhang JX, et al. Loss of vaccine-induced immunity to varicella over time. N Engl J Med 2007;356:1121-1129.

Study Design:
Cohort (prospective)

Synopsis:
The introduction of universal varicella vaccination in 1995 has substantially reduced varicella-related morbidity and mortality in the United States. However, it remains unclear whether vaccine-induced immunity wanes over time, a condition that may result in increased susceptibility later in life, when the risk of serious complications may be greater than in childhood. They examined 10 years (1995 to 2004) of active surveillance data from a sentinel population of 350,000 subjects to determine whether the severity and incidence of breakthrough varicella (with an onset of rash >42 days after vaccination) increased with the time since vaccination. We used multivariate logistic regression to adjust for the year of disease onset (calendar year) and the subject’s age at both disease onset and vaccination. A total of 11,356 subjects were reported to have varicella during the surveillance period, of whom 1080 (9.5%) had breakthrough disease. Children between the ages of 8 and 12 years who had been vaccinated at least 5 years previously were significantly more likely to have moderate or severe disease than were those who had been vaccinated less than 5 years previously (risk ratio, 2.6; 95% confidence interval [CI], 1.2 to 5.8). The annual rate of breakthrough varicella significantly increased with the time since vaccination, from 1.6 cases per 1000 person-years (95% CI, 1.2 to 2.0) within 1 year after vaccination to 9.0 per 1000 person-years (95% CI, 6.9 to 11.7) at 5 years and 58.2 per 1000 person-years (95% CI, 36.0 to 94.0) at 9 years.